Some GMC engines, including 228s, I think, had domed pistons and a different combustion chamber shape to the head. Others were flat tops and a different head. 228 and 248 have the same stroke crankshaft, but different bore sizes. Ditto for 270 and 302- - - -both 4" stroke.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!